The SUMO System: An Overview

Post-translational modification by SUMO is now recognized as an important regulatory method employed by the cell to reversibly modulate the activity, stability, or localization of intracellular proteins. A dedicated enzymatic machinery is involved in the processing, attachment, and removal of the modifier with high selectivity. SUMO modification generally alters the properties of the modified target by influencing—either positively or negatively—its interactions with other cellular factors. As a consequence, the SUMO system contributes to the regulation of numerous biological pathways, ranging from nucleocytoplasmic transport to the repression of transcriptional activity and the maintenance of genome stability by its influence on DNA recombination and repair. This chapter gives a brief overview over the enzymes of the SUMO system, its regulation, and its functions.